Problem: If $a + b + c = 9$ and $x + y = -5$, what is $3c - 7x + 3a - 7y + 3b$ ?
Explanation: $= 3a + 3b + 3c - 7x - 7y$ $= (3) \cdot (a + b + c) + (-7) \cdot (x + y)$ $= (3) \cdot (9) + (-7) \cdot (-5)$ $= 27 + 35$ $= 62$